This application is directed to a method of treating colonic adenomas by administration of a non-toxic therapeutically effective amount of an non-steroidal anti-inflammatory agent (NSAID). In particular, this application is directed to a method of preventing or retarding the transformation of colonic adenomas to colonic adenocarcinomas by administration of a non-toxic therapeutically effective, specific PGHS-2 inhibitor.
The enzyme prostaglandin G/H synthase (PGHS) is a key enzyme in the biosynthetic pathway leading to the formation of prostaglandins (Watkins, W. D., Peterson, M. B., and Fletcher, J. R. ed. Prostaglandins in Clinical Practice. New York: Raven, 1989 and Dewitt, D. L. Prostaglandin endoperoxide synthase: regulation and enzyme expression. Biochim. Biophys. Acta, 1083; 121-134, 1991). These prostanoids are potent biological mediators with diverse normal physiological effects and are also implicated in a variety of pathological conditions including inflammation and neoplastic transformation (Watkins, W. D., Peterson, M. B., and Fletcher, J. R. ed. Prostaglandins in Clinical Practice. New York: Raven, 1989 and Dewitt, D. L. Prostaglandin endoperoxide synthase: regulation and enzyme expression. Biochim. Biophys. Acta, 1083; 121-134, 1991 and Xie, W., Robertson, D. L., and Simmons, D. L. Mitogen-inducible prostaglandin G/H synthase: a new target for nonsteroidal anti-inflammatory drugs. Drug Dev. Res., 25; 249-265, 1992). Two isoforms of PGHS have been identified (Loll, P. J. and Garavito, R. M. The isoforms of cyclooxygenase: structure and function. Expert Opin. Invest. Drugs, 3; 1171-1180, 1994). PGHS-1 is constitutively expressed in most tissues and has been proposed to generate prostaglandins for normal physiological functions. The second isoform, PGHS-2, is characterized by a rapid induction by a variety of stimuli, including mitogens, hormones, cytokines and growth factors (Loll, P. J. and Garavito, R. M. The isoforms of cyclooxygenase: structure and function. Expert Opin. Invest. Drugs, 3; 1171-1180, 1994 and Battistini, B., Botting, R., and Bakhle, Y. S. COX-1 and COX-2: Toward the development of more selective NSAIDS. Drug News Perspectives, 7; 501-512, 1994). In conditions such as inflammation, PGHS-2-derived prostaglandins may be the predominant effectors (Masferrer, J. L., Zweifel, B. S., Manning, P. T., Hauser, S. D., Leahy, K. M., Smith, W. G., Isakson, P. C., and Seibert, K. Selective inhibition of inducible cyclooxygenase 2 in vivo is anti-inflammatory and non-ulcerogenic. Proc. Natl. Acad. Sci. USA, 91; 3228-3232, 1994). Both PGHS-1 and PGHS-2 have been shown to be the target of nonsteroidal anti-inflammatory drugs (NSAIDs) (Battistini, B., Botting, R., and Bakhle, Y. S. COX-1 and COX-2: Toward the development of more selective NSAIDS. Drug News Perspectives, 7; 501-512, 1994 and O'Neill, G. P., Mancini, J. A., Kargman, S., Yergey, J., Kwan, M. Y., Falgueyret, J. -P., Abramovitz, M., Kennedy, B. P., Ouellet, M., Cromlish, W., Culp, S., Evans, J. F., Ford-Hutchinson, A. W. and Vickers, P. J. Overexpression of human prostaglandin G/H synthase-1 and -2 by recombinant vaccinia virus: inhibition by nonsteroidal anti-inflammatory drugs and biosynthesis of 15-hydroxyeicosatetraenoic acid. Mol. Pharmacol., 45; 245-254, 1994 and DeWitt, D. L., Meade, E. A., and Smith, W. L. PGH synthase isoenzyme selectivity: the potential for safer nonsteroidal anti-inflammatory drugs. Am. J. Med. (Suppl.), 95; 40S-44S, 1993). See also WO 94/14977, published Jul. 7, 1994, which discloses a method of evaluating the potency of PGHS-2 inhibiting agents as well as the selectivity for PGHS-2 over PGHS-1.
Elevated levels of prostaglandins have been demonstrated in various cancers including lung and colon carcinomas (McLemore, T .L., Hubbard, W. C., Litterst, C. L., Liu, M. C., Miller, S., McMahon, N. A., Eggleston, J. C., and Boyd, M. R. Profiles of prostaglandin biosynthesis in normal lung and tumor tissue from lung cancer patients. Cancer Res., 48; 3140-3147, 1988 and Rigas, B., Goldman, I. S., and Levine, L. Altered eicosanoid levels in human colon cancer. J. Lab. Clin. Med., 122; 518-523, 1993). In particular, prostaglandin levels have been shown to be elevated in benign adenomatous polyps and further increased in cancerous colon tissue, as compared to histologically normal mucosa. Since prostanoids have been shown to be immunosuppressive, they may play a role in tumor development (Earnest, D. L., Hixson, L. J., and Alberts, D. S. Piroxicam and other cyclooxygenase inhibitors: potential for cancer chemoprevention. J. Cell. Biochem., 161 (Suppl.); 156-166, 1992).
Since the late 1970's, investigators have considered the possibility that aspirin and related nonsteroidal anti-inflammatory drugs (NSAIDs) might be beneficial to the treatment of certain cancers, including colon cancer.
The first epidemiological study suggesting that aspirin might reduce the risk of colorectal cancer came in 1988 in a retrospective, exploratory analysis from Melboum, Australia (Cancer, Res., 48: 4399-4404, 1988). The study found a 40 percent lower risk of incident colon cancer among persons who regularly used aspirin compared to those who used no aspirin. More recently the data of Heath, et al, suggests the possible benefit of NSAIDs for prevention of colorectal neoplasms (Heath, C. W., Jr., Thun, M. J., Greenberg, E. R., Levin, B., and Marnett, L. J. Nonsteroidal anti-inflammatory drugs and human cancer. Cancer, 74; 2885-2888, 1994). However, despite this and subsequent studies, there has been no hard evidence linking the use of and the prevention of colon cancer, nor has there been any hard evidence demonstrating a pathological link between colorectal cancer and PGHS or the therapeutic value of inhibiting PGHS by administration of aspirin. For example, arthritis patients (many of whom take aspirin) may simply be less prone to cancer of the colon.
In this application we disclose studies in which we have analyzed the expression of human PGHS-1 and PGHS-2 protein in 25 paired normal and autologous colon tumors, 4 premalignant colon polyps, 5 control colon tissues (from non-cancer patients) and 3 matched normal and cancerous human breast tissues. Among the observations from this study are that PGHS-1 protein is reduced in colon tumor tissue as compared to histologically normal colonic mucosa, and that PGHS-2 is detected in the majority of colon tumor samples while being virtually undetectable in normal tissues, polyps and breast cancer samples. The increased levels of prostaglandins in tumor tissue of the colon is derived from the inducible PGHS-2 isoform. These studies support our belief that the transformation of a colonic adenoma to a colonic adenocarcinoma is mediated by the dramatic and surprising over production of PGHS-2 in the adenoma. Accordingly, we have surprisingly found a method of retarding or preventing the transformation of a colonic adenoma to an colonic adenicarcinoma comprising the administration to a patient with a history of FAP (Familial adenomatous Polyposis) or a patient with one or more colonic adenomas a non-toxic therapeutically effective amount of NSAID; said amount effective to inhibit the PGHS-2 in said adenoma.